Microchip fabrication is a cornerstone of modern technology. As integrated circuits ("ICs") have become staple items in devices in all areas, the fabrication process for ICs has developed rapidly. Central to the fabrication process is the patterning of a substrate in accordance with the configuration of a desired feature set.
Conventional patterning typically utilizes photolithography in the patterning process. Multiple forms of photolithography are commonly used. Each includes several similar basic steps. A photoresist film is applied to a substrate surface to be patterned. Photoresist is a light-sensitive material that has properties which change upon exposure to light. A mask is then aligned to the substrate. The mask contains a pattern of the desired pattern to be transferred to the substrate. The photoresist film is then exposed to light, where the mask obscures portions of the photoresist from the light. A developer or solvent is then applied to remove a portion of the photoresist, according to the reaction of the photoresist to exposure. An etchant is applied again to pattern the substrate through the holes formed in the photoresist. Finally, any remaining photoresist is stripped away, leaving a patterned substrate.
A significant limitation of photolithography is the resolution capability of optical photolithography. The smallest openings which are created are limited by the smallest areas which can be defined by the mask and exposure on the photoresist. Conventional photolithography is typically limited to about 125 to 200 micrometers. As resolution capability improves, the number of devices which may be included in a single IC increases, improving the efficiency and performance of the IC. In addition, improved resolution capability typically raises wafer yield.
Alternate forms of resist may be used in lithographic processes. Photoresist changes in response to exposure to light. Other resists change in response to different events. Some resists alter in response to an electric field applied to the resist.
Accordingly, the inventors have determined that it would be desirable to provide a device for lithography which has an improved resolution capability relative to conventional photolithography technology using modification of an electric field to alter a resist for lithographic patterning.